1. Field of the Invention
The present invention relates generally to grinding wheels used to grind work rolls used in the production of metal sheet material, such as aluminum sheet. More specifically, the present invention relates to an apparatus and method for inspecting grinding wheels used in the production of metal sheet material.
2. Description of Related Art
A problem in the production of metal sheet material (hereinafter “metal sheet”), such as aluminum sheet, is the introduction of a pattern onto the metal sheet during rolling operations. The “patterning” introduced onto the metal sheet is caused by the work rolls used in rolling operations. The patterning caused by the work rolls is introduced onto the work rolls during preparation of the work rolls for rolling operations. Typically, the work rolls are ground to meet certain pre-established parameters, such as surface roughness, using grinding wheels. Accordingly, if the grinding wheels contain certain defects, these defects are transferred to the work rolls during grinding operations.
As stated, patterning is imprinted onto the work rolls during grinding and is transferred or imprinted onto the metal sheet during rolling operations. Metal sheet containing imprinted patterns is not suitable for sale for surface sensitive products and may be scrapped. The undesired “imprinted” work rolls must then be changed and reground. This results in considerable downtime on the production line and significant monetary loss when a finished metal coil is scrapped.
It is known in the art that for nominally identical grinding wheels some grinding wheels used to prepare work rolls are better to use than others. By better, it is meant that the required work roll roughness specification and other desired parameters may be obtained without introducing patterning onto the work roll, which is then imprinted onto the rolled metal sheet during production. Some grinding wheels cause a great amount of patterning and obtaining the desired roughness specification and other parameters on the work rolls is often difficult or impossible.
Numerous systems and methods are known in the art for generally inspecting the surface quality and other parameters of materials using ultrasound, lasers, and the like. For example, U.S. Pat. No. 6,182,499 to McFarland et al. discloses a method and apparatus for determining the surface quality of an array of materials through the use of acoustical waves. U.S. Pat. No. 5,852,233 to Arnold et al. discloses an acoustic microscope that measures both the typography and elasticity of a material substrate by measuring the deflection of a laser beam. U.S. Pat. No. 4,991,124 to Kline discloses a method for determining the density of a liquid by measuring the amplitude of the reflections of ultrasonic pulses introduced into the liquid. A transducer is used to transmit an ultrasonic pulse through the liquid to a reference material provided in the liquid that is of known density. U.S. Pat. No. 4,969,361 to Kawasaki et al. discloses an ultrasonic device for detecting defects of structural balls. The ball to be tested is provided in a water tank that is filled with water, which is used as the ultrasonic conducting medium. The transducer emits sound waves that are echoed back to the transducer while the ball is rotating in the liquid medium to scan for defects in the ball.
U.S. Pat. No. 4,738,139 to Blessing et al. discloses an ultrasound device that is used to measure surface characteristics such as roughness, scratches, and dents in a substrate. The ultrasound device sends ultrasonic waves through a fluid, which is in laminar flow along a curved path. U.S. Pat. No. 4,603,583 to Heumüller discloses an ultrasonic testing apparatus for testing feritic bodies having a cladding surface. An ultrasound transmitter radiates from a surface opposite the cladding surface into the body at an angle relative to the cladding surface. A receiver receives the reflections emanating from any faults in the body. U.S. Pat. No. 4,364,264 to Re Florentin discloses an ultrasonic device for measuring the degree of roughness of an uneven surface. The ultarsonic device includes a transmitting transducer that propagates sound waves through a liquid coupling medium onto the surface being examined. The ultrasonic device further includes a receiving transducer, which receives reflected waves from the surface being examined.